1. Field of the Invention
The invention generally relates to heat sinks for electronic circuits. More specifically, the field of the invention is that of attachment arrangements for maintaining thermal connection between electronic circuitry and heat sinks such as in power transformers and amplifier circuits for automobiles and other vehicles and other applications.
2. Description of the Related Art
In conventional vehicle power converters, such as those transformers and amplifier circuits for automobiles and other vehicles, the power transistors and rectifiers are used to scale down AC line voltage to suitable 12 volt DC currents. As a result of this step down transformer circuitry, the power transistors and rectifiers used in the circuit generate substantial amounts of heat. Conventionally, the casings of these units are built with heat sinks, typically on the lateral walls, so that the heat generated by the electrical components can be dissipated. Because of the space limitations in the vehicles, these casings are configured to minimize the amount of space occupied, resulting in the electrical components being closely positioned together within the casing often with little or no internal ventilation. The heat generating electrical components are placed into contact with the heat sink to dissipate the generated heat. In order to maximize the heat dissipation of the heat sink, it is important to maintain the direct physical contact of the power transistor or rectifier component against the heat sink material of the casing.
A conventional method of mounting the power transistor or rectifier components to the heat sink includes drilling a hole in the heat sink material and screwing down the component. Typically, this requires a physical extension of the component which is large enough to have a screw hole, and which is rigid enough to hold the body of the component against the heat sink when the screw fastens the component down. One difficulty with this arrangement involves matching the locations of the component screw hole and the hole of the heat sink, because the component is usually located at a fixed position on the circuit board. These complications can interfere with the quality of the connection of the component with the heat sink, can stress the electrical connections, as well as increasing the time needed to manufacture the unit.
Alternative methods of maintaining the thermal connectivity of the component and the heat sink involve screwing down a hold down bar or a clamp to hold the component in place, or forming a screw hole or channel in the power transistor or rectifier component so that the component may be directly screwed to the heat sink. These methods similarly have disadvantages in terms of material cost, manufacturing cost, and heat dissipation effectiveness. The additional cost of the screw and allocating manufacturing resources to providing the hole for the screw and the labor to install the screw increase the cost of the unit. Any loosening of the set screw will decrease the thermal connectivity of the component with the heat sink. Further, the location and placement of the screws must be carefully made so that other portions of the transformer or amplifier are not damaged.
Similar problems confront other types of electrical circuit devices. Computers, telecommunications equipment, medical imagining equipment, and other types of electronics include package semiconductors which generate heat during operation. Many varieties of clamping devices, some spring activated, are used in such circuitry to hold a semiconductor package in thermal contact with the heat sink. Typically, additional structural elements are needed on the semiconductor package or the circuit board to create the clamping effect. However, these required additional structural elements prevent such arrangements from being used with conventional semiconductor package or circuit board configurations.
What is needed is an effective method of maintaining the thermal connectivity of the heat generating component to the heat sink wall.